What is "spent ball"

Spent \Spent\ (sp[e^]nt), a.

1. Exhausted; worn out; having lost energy or motive force.

   Now thou seest me Spent, overpowered, despairing of success.
   --Addison.

   Heaps of spent arrows fall and strew the ground.
   --Dryden.

2. (Zo["o]l.) Exhausted of spawn or sperm; -- said especially of fishes.

   Spent ball, a ball shot from a firearm, which reaches an object without having sufficient force to penetrate it.